1. Field of the Invention
This invention relates to a support assembly for non-metallic cable comprising a metallic support fitting and a metallic stress limiter for relieving electrical stress between the cable and the support fitting, and is particularly useful with optical aerial cables which are positioned adjacent high voltage power lines.
2. Description of Related Art
As disclosed for example in a paper entitled "Experience with Optical Fibre Aerial Cables on High Tension Power Lines" by C. Jurdens, H. G. Haag and R. Buchwald, given at the Cigre International Conference on Large High Voltage Electric Systems, 1988 Session, non-metallic self-supporting overhead optical cables are supported adjacent towers at respective fixing points along the cable by means of preformed metallic fittings comprising helical wires which form a sheath around the cable and grip it tightly. Stress limiters in the form of toroidal control electrodes prevent corona discharge at the ends of the helical wires. These electrodes are commonly formed of wire wound into a toroidal cage whose centre ring connects mechanically and electrically with the ends of the cable support fitting furthest from the tower.
This known type of stress limiter is expensive to make and, more importantly, difficult to fit in situ. Further, it has been recognized that it is a combination of electrical and mechanical stresses at the interface of the cable and the support which causes degradation and ultimately failure of the cable in this critical area, where the cable is close to a power cable and where the optical cable support is grounded by the tower, and especially in weather conditions such that the optical cable is partly wet and partly dry.